1 files changed, 15 insertions, 1 deletions
diff --git a/clang/lib/AST/ItaniumMangle.cpp b/clang/lib/AST/ItaniumMangle.cpp
index e51aad9ad83..1fcf466a1f6 100644
--- a/clang/lib/AST/ItaniumMangle.cpp
+++ b/clang/lib/AST/ItaniumMangle.cpp
@@ -2055,9 +2055,23 @@ void CXXNameMangler::mangleType(const FunctionProtoType *T) {
 
   Out << 'E';
 }
+
 void CXXNameMangler::mangleType(const FunctionNoProtoType *T) {
-  llvm_unreachable("Can't mangle K&R function prototypes");
+  // Function types without prototypes can arise when mangling a function type
+  // within an overloadable function in C. We mangle these as the absence of any
+  // parameter types (not even an empty parameter list).
+  Out << 'F';
+
+  FunctionTypeDepthState saved = FunctionTypeDepth.push();
+
+  FunctionTypeDepth.enterResultType();
+  mangleType(T->getReturnType());
+  FunctionTypeDepth.leaveResultType();
+
+  FunctionTypeDepth.pop(saved);
+  Out << 'E';
 }
+
 void CXXNameMangler::mangleBareFunctionType(const FunctionType *T,
                                             bool MangleReturnType) {
   // We should never be mangling something without a prototype.